Most passenger restraint devices employ safety belts that are wound upon automatic, emergency locking safety belt retractors that are secured to the vehicle frame. With use of these retractors, the reels lock in response to a relatively high, abnormal acceleration or deceleration of the vehicle. However, emergency locking retractors allow a rather considerable extension of safety belt webbing, even though the reel is locked, because the several turns of the belt webbing normally on the reel are initially loose until pulled tight when the passenger is thrown forward and also because the belt webbing itself elongates.
Various types of locking means have been used to avoid the extension of the safety belt webbing. However, these have been unsatisfactory because they allow the belt to slip or they preset a risk of belt failure because they cut or dig into the belt. In other instances, the lock can be so effective that it is difficult to release the belt, thus causing greater danger to the occupant when there is need for rapid escape from the vehicle after an accident. Further still, some locking means employ an increased spring force which makes the belt more difficult to fasten and unpleasant to wear, because the belt exerts a heavier pressure on the occupants chest.
This seat belt webbing extension and slack is particularly problematic in rollover accidents. In a typical rollover event, the vehicles occupants experience lateral decelerations prior to encountering any rotational motion. During this lateral deceleration phase, the resulting occupant motion can cause the seat belt to slide off the occupants shoulder and generate slack in the lap belt portion of the seat belt. Therefore, as the occupant begins to experience rotational and vertical motion, this additional lap belt slack hinders the effectiveness of the lap belt and allows the occupant to move vertically out of position and either strike the vehicle's roof or be ejected from the vehicle.
It would therefore be beneficial to have a device that improves the effectiveness of a standard three-point belt system by minimizing a belted occupants vertical excursion and reducing the possibility of ejection from a vehicle in the event of a rollover accident by reducing the amount of belt slack transferred to the lap portion of the seat belt.
Therefore, it is desired to have a safety belt webbing emergency locking device that provides a quick restraint of the safety belt in the event of an emergency, and particularly a rollover event, while also reducing lap belt slack and any belt webbing extension after actuation, without damaging the webbing.